internal: Get rid of the whole "sub cache" business. * Compute cache keys up front, so the cache directory is only chosen once. * Buffer up config variants to apply before loading the config. Makes it possible to cache variant-resulting configs, too. * Make a factory class to reuse the logic that creates the `PieCrust` object correctly for multi-process workers and such. * Add a test.

{% extends "default.html" %}

{% block content %}
<div class="container">
    <section class="col-md-8">
    {{ content|safe }}
    </section>
    <aside class="col-md-4">
        {% include 'inc/family-sidebar.html' %}
    </aside>
</div>
{% endblock %}